But on its own B-movie terms 47 Meters Down works just fine, not wearing out its welcome thanks to its quick set-up, rapid pacing and brief running time.

It's not a great film but, once the preliminary scenes on terra firma are over and we descend to a place we don't belong, it delivers an hour or so of sustained physical and psychological terror.

British director Johannes Roberts makes decent use of the murk (the film was largely shot in a tank in London) and the sisterhood theme gives the film a broader appeal than, say, The Shallows.

The four leads are fine. This feels like a collective of Hollywood kids who got a lucky break on Bring Your Daughter to Work Day.